1. Field of the Invention
The present invention relates to a recording apparatus adapted for high-speed print-out of characters, graphic information, etc. supplied particularly from computers. The word `recording apparatus` herein used should be understood in the widest sense and includes printing and copying apparatus.
2. Description of the Prior Art
Although mechanical impact printers have been most widely utilized as the output device for computers, the recent advancement in the electronic technologies and the resulting increase in the processing capacity of calculating devices and memories require the development of output printers with a performance superior to that of conventional mechanical impact printers. Though there have been developed various non-impact printers to respond to this requirement, particularly advantageous, in consideration of speed, print quality and running cost, is the so-called transfer type electrostatic or electrophotographic recording process in which, as disclosed for example in the U.S. Pat. No. 3,358,081, an electrostatic latent image corresponding to the information from a computer etc. is formed on an image carrying member such as a photosensitive member and developed into a visible image with a toner material, said visible image being transferred onto a plain paper sheet (recording material) and fixed thereon to obtain a final output consisting of toner image fixed on a plain paper.
In such an electrophotographic recording process, and as a means for fixing toner onto a recording paper (including various forms of paper such as fan-fold form and continuous roll form) there is usually employed a mechanism consisting of a heated fixing roller and a back-up roller maintained in pressure contact, through said paper, with said fixing roller. In such mechanism threading of paper between said rollers is difficult to achieve in a manual operation since the fixing roller is maintained at a high temperature (for example ca. 180.degree. C.).
Also a transfer charger is generally provided in the transfer position of toner image onto paper, and it is quite cumbersome, in case of perform recording from perforations on the paper, namely from the leading end of a page, to maintain said perforations in register with said transfer position.
Furthermore there exists a similar concern in case of restarting the advancement of paper after a temporary stop, for example for achieving an exact synchronization with other processing means.
Furthermore, in such a process, the position of information recording on a photosensitive member to form an electrostatic latent image thereon is generally different from the position of image transfer from said photosensitive member onto a sheet, and, also along the path of said recording sheet, said transfer and said fixing are generally conducted in different positions.
Thus, even if the recording process is interruped upon detection of the trailing end of a recording sheet, the transfer step has to be continued thereafter since there still exists, on the photosensitive member, an electrostatic latent image and a toner image which is not yet transferred.
In order to complete the transfer of said electrostatic latent image and the untransferred toner image, there is naturally required a margin on the recording sheet of a length equal to the distance between the recording position and the transfer position both on said photosensitive member. Stated differently the detector for the trailing end of the transfer sheet is required to be provided in a position far enough from said transfer position to assure said margin on the transfer sheet.
Such requirement, resulting from the above-mentioned distance between the transfer and fixing positions and also from the distance between said transfer position and the conveyor means for the transfer sheet, has been accommodated, conventionally, by placing the unprinted transfer sheet in a position distanced by a necessary length from said conveyor means, sacrificing the compactness of the apparatus.